Illinois Architect seal requirements: size, wording, and the rule that sets them

Yes, and that is where it parts company with the engineer's. The architect's seal carries the name of the architect, the license number, and the words "Licensed Architect, State of Illinois", while the engineer's rule at 68 Ill. Adm. Code § 1380.295 requires "Licensed Professional Engineer of Illinois". One says "State of Illinois" after a comma, the other says "of Illinois"; the two are not interchangeable, and no diameter is prescribed for either. (68 Ill. Adm. Code § 1150.ILLUSTRATION A(a); § 1380.295(a))

Only the first, but it has to declare its own scope. The rule requires the signature, current date, date of license expiration and seal to be affixed to the first sheet of any bound set or loose sheets of technical submissions used as contract documents or prepared for the review and approval of a governmental or public authority — and then adds that the sheet on which the seal is affixed "shall indicate those documents or parts of documents for which the seal shall apply". A sealed cover sheet with no such indication leaves out half the requirement. (68 Ill. Adm. Code § 1150.ILLUSTRATION A(a))

The individual architect's, and it falls on November 30 of an even-numbered year: every license issued to an individual under the Act expires on November 30 of each even-numbered year, which is why the suggested facsimile in the rule prints the expiration line as 11-30 with the year left blank. A design firm's registration runs on an entirely different cycle, expiring April 30 of each odd-numbered year, and what the firm contributes to the documents is its corporate or assumed business name and design firm registration number — not its expiration date. (68 Ill. Adm. Code § 1150.100(a), (c); § 1150.ILLUSTRATION A(a), (b), (c); § 1150.80(h))

Both architects', in different places. Prototypical documents may be prepared by an architect licensed in any jurisdiction, and the first sheet of the set must be identified as "prototypical documents" and carry the name, address and seal of the architect who prepared them, together with the date they were prepared. The Illinois licensed architect then issues the technical submissions for construction under his or her own title block, Illinois seal and design firm registration number — after obtaining written permission from both the preparing architect and the legal owner of the documents, and independently performing and keeping on file the calculations and analysis verifying the original design. (68 Ill. Adm. Code § 1150.85(d)(2), (d)(3), (d)(4))

It can, but it does not relieve the consultant. An architect may sign and seal portions of the professional work prepared by consultants licensed under another professional licensure law of Illinois if the architect has reviewed the portion, coordinated its preparation and intends to be responsible for its adequacy — and the rule then states that this "does not exempt the consultant from signing and sealing professional work prepared by the consultant". Both seals belong on the set. The permission runs only to consultants licensed in this jurisdiction; outside that, the architect must have exercised responsible control. (68 Ill. Adm. Code § 1150.90(e)(1))